I called MFJ today to try to figure out what the differences between the 1708 and the 1708B SDR switches. Customer service did not know so they suggested I call technical service. When I spoke to technical service they said the difference was that the B model had four relays in it instead of one. The obvious question then was OK so why is that better? His response was, “ gosh I guess I don’t really know”. And that would’ve been his only offering had I not pushed him to find out more. You put me on hold for a minute and came back and said “well I guess I can see that it we added some LED lights to it and some more relays.”

So, I was going to ask you guys if anybody knew more than MFJ does about their own product but I guess I would prefer to find one built by somebody else. Is there another offering available?

Gee, you made me go look..
downloaded the manuals for both..
the 08 has so239 connectors and no rf sensing is basically a plain t/r switch.
the 08b can be had with an SMA for the sdr feed.
from the man:
The MFJ-1708B-SDR and the MFJ-1708B-SDRS are RF sensed TR switches with a
receive splitter designed to be used with a transceiver and a separate receiver such as
the popular SDR receivers. The splitter give high isolation between the transceiver and
SDR Receive port to reduce crosstalk and interference between the two ports. The SDR
port has a protection circuit to help prevent damage from transmit RF. The MFJ-1708BSDR
has a Stripline PCB reducing the SWR up through 450MHz and improved isolation
for better receiver protection.
MFJ-1708B-SDRS has an SMA connector for ease of connection to SDR dongle
receivers.